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Embryo E1 > Review > Flashcards

Review Flashcards

1
Q

What stage of meiosis does crossing over occur?

A

Pachytene

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2
Q

What is trisomy?

A

An extra chromosome of non-sex chromosome; caused by a nondisjunction

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3
Q

What is monosomy?

A

lack of a chromosome of non-sex chromosomes; caused by a non-disjunction

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4
Q

What is aneuploidy?

A

Abnormal number of chromosomes

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5
Q

What is polyploidy?

A

more than two complete sets of chromosomes

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6
Q

During oogenesis, when does the second meiotic arrest occur?

A

Metaphase II

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7
Q

Which hormone is required for rapid transport of the egg through the isthmus of the oviduct?

A

Progesterone

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8
Q

What is the fate of most female germ cells?

A

Many will become atretic

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9
Q

What is the difference between theca externa and theca interna?

A

Externa: produces angiogenesis factor

Interna: LH receptors, secrete testosterone

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10
Q

What structures form the corpus luteum?

A

Residual theca and granulosa cells

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11
Q

What is the function of aromatase?

A

Converts testosterone into 17beta-estradoil

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12
Q

What hormone stimulates formation of LH receptors on granulosa cells?

A

Estrogen

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13
Q

What changes to the sperm occur in the head of the epididymis?

A

Changes in glycoproteins in the plasma membrane of the sperm head. Sperm are capable of fertilization by the time they reach the tail of the epididymis.

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14
Q

A surge in which hormone level occurs 24 hours prior to ovulation?

A

LH

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15
Q

What is the fate of the follicle if no fertilization occurs?

A

corpus luteum regresses, progesterone and estradiol levels drop, and menstruation begins.

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16
Q

What is the fate of the follicle if fertilization occurs?

A

HCGn from future placental tissues maintains the corpus luteum, which remains functional for several months into pregnancy.

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17
Q

What is the role of inhibin in relation to the ovarian cycle?

A

Inhibin inhibits secretion of gonadotropins, like FSH, resulting in the regression of the corpus luteum.

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18
Q

What is the most likely site of fertilization?

A

ampulla

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19
Q

Compare fertilization and menstrual age with regard to establishing the age of the embryo?

A

Fertilization is the age of the embryo from fertilization where as menstrual age is the age of the embryo from the last menstruation period.

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20
Q

What is the major action of hyaluronidase?

A

It is one of the major enzymes in the acrosome. It helps break down the hyaluronic acid component of the intracellular matrix between the corona radiata cells.

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21
Q

Define zygote?

A

Term used to denote the single celled stage at which the male and female pro-nuclei have fused together and share a common membrane, establishing the diploid chromosome number.

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22
Q

What is the characteristic of fast block to polyspermy?

A

Rapid depolarization of egg plasmalemma

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23
Q

What is the characteristic of slow block to polyspermy?

A

Mostly characterized by the release of polysaccharides from the cortical granules located just under the plasmalemma of the egg.

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24
Q

What is the function of ZP3?

A

stimulates acrosomal reaction in mammals, causing a massive influx of calcium ions through the sperm plasma membrane, and sodium exchanged for hydrogen ions that increase pH which allows the sperm to penetrate the zona pellucida.

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25
Q

What is the function of phospholipase C?

A

metabolic egg cell activation is initiated by the release of calcium ion within egg cytoplasm in response to introduction of phospholipase C.

26
Q

What ions initiates metabolic activation of the egg? What are the results of this activation?

A

Calcium; it initiates blocks to polyspermy.

27
Q

What gene is involved in the initiation of cleave and the first cleavage division?

A

Oct-4 is required to permit cleave to the 2-cell stage.

28
Q

What is the general structure of the blastocyst?

A
  • approx. 58 cell stage
  • surrounded by zona pellucida
  • large, eccentrically place blastocoel
  • consists of two types of cells (trophoblast and inner cell membrane).
29
Q

What is the function of nanog?

A
  • Produced by inner cell mass and maintains the integrity of the inner cell mass.
  • without nanog, cells differentiate into endoderm
30
Q

What is the function of Sox2?

A

First expressed in 8 cell stage, and helps control the regulation of genes involved in differentiation.

31
Q

What is the function of Cdx2?

A

Essential for trophoblast cell differentiation.

antagonistic towards oct4

32
Q

At what point in development does most transcription via the embryonic genome begin to occur?

A

Maternal gene products are degraded by the two cell stage. By the four cell stage, most transcription is via the embryonic genome.

33
Q

At what point during early development is methylation the lowest?

A

During fertilization up to the morula stage.

34
Q

What is the inside-out model?

A

The fate of the blastomere is determined by its position within the embryo

35
Q

What is the cell polarity model?

A

The plane of cleavage decides what the cells will become

36
Q

What is the function of oct4?

A
  • required to proceed to the two cell stage
  • expressed in morula (eight cell stage)
  • may play a role in the maintenance of the undifferentiated state.
37
Q

From which parent is Prader-Willi syndrome inherited?

A

father

38
Q

From which parent is Angelman syndrome inherited?

A

mother

39
Q

What does Bateson’s rule refer to?

A

States that when duplicated structures are joined during critical development states, one structure is the mirror image of the other.

40
Q

What is the definition of regulation, and how is it related to twinning?

A
  • the ability of an embryo or organ primodium to produce a normal structure if parts have been added or removed.
  • twins arise by the splitting of the inner cell mass.
41
Q

What role does xist play?

A

xist is an X inactivation specific transcript.

42
Q

When does x inactivation occur?

A

during the first few weeks of development.

43
Q

Describe the trophoblast and relate to its two main divisions. Which division directly interfaces with the endometrial connective tissue?

A
  • trophoblast is composed of the cytotrophoblast and the syncytiotrophoblast.
  • syncytiotrophoblast projections penetrate the endometrial basal lamina and then begin to invade the endometrial stroma.
44
Q

What is the process of implantation?

A

(starts at day 6)

  • attachment of expanded blastocyst to the endometrial epithelium
  • Penetration of the uterine epithelium
  • invasion into the tissues underlying epithelium
  • erosion of the maternal vascular supply
45
Q

What is the most common site for ectopic pregnancy?

A

ampulla of the fallopian tube

46
Q

What might occur if the decidual reaction does not take place?

A

the trophoblast may potentially erode all the way through the endometrial wall.

47
Q

What is the function of egg polarity?

A

important in the establishment of the dorsal-ventral and anterior-posterior axis in the fruit fly.

48
Q

What is the function of gap genes?

A

delete adjacent segments

49
Q

What is the function of the pair rule?

A

same part of the pattern in every other segment

50
Q

What is segment polarity?

A

affect polarity of the segment

51
Q

What are homeotic genes?

A

determine the identity of individual segments. Products of homeotic genes activate other genes that encode these specific characteristics.

52
Q

What is a morphogen?

A

A protein that varies in concentration and causes different developmental responses as a result of the concentration differences

53
Q

What are bottle cells and what role do they play in gastrulation?

A

They are cells that migrate through the primitive streak.

Bottle cells drive gastrulation

54
Q

What are the two major signaling molecules that play a role in the formation of the primitive streak?

A

TGF-B and Wnt1

55
Q

What tissues are derived from the hypoblast?

A

Membranes that surround and protect the embryo

56
Q

What tissues are derived from the epiblast?

A

ectoderm, mesoderm and endoderm

57
Q

When does gastrulation occur in humans?

A

At the end of the second week of gestation

58
Q

What factor represents the first sign of asymmetry in the mammalian embryo?

A

the beating of the cilia around the primitive node

59
Q

Which signal molecule is expressed by the isthmic organizer?

A

wnt1, FGF8, En1, En2

60
Q

Describe a loss-of-function mutation.

A

Loss-of-function mutations result in posterior to anterior transformations. Cells in a given segment form the structural equivalent of the next most anterior structure.

61
Q

Describe a gain-of-function mutation.

A

Gain-of-function mutations result in anterior to posterior transformations.

62
Q

What signaling factor family is related to segment polarity molecules in fruit flies?

A

hedgehog

Embryo E1 (2 decks)

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